House and roof collapse in Mascot: raw vision

An elderly man was lucky to escape unharmed after his house partially collapsed in Mascot in Sydney's south east on Wednesday.

Emergency services are still working to secure the rest of the buckling property and to retrieve three cats believed to be inside when the roof gave way.

NSW Fire and Rescue Superintendent Tom Cooper said the elderly man was inside the King Street house when part of the roof started collapsing and falling onto the house next door.

Fire crews were called to the scene just after 2.15pm. There are no reports of injuries and paramedics were not contacted.

"A veranda roughly 10 by two metres seems to have collapsed at the side of the building, taken down the outside skin of the wall, caused a chimney to fall out, which has caused the roof of the house to collapse," Superintendent Cooper said. "It's fallen onto the property next door and that's caused the rest of the roof to come down."

An exclusion zone around the house has been established and engineers and specialist urban search and rescue firefighters are making an assessment of the building.

Picture: Nine News

Superintendent Cooper said the building was being considered "unstable" and he were concerned it would further crumble, with a gable looking like it might give way. Electricity, gas and water have been cut off to the house.

The house was an old building, one of few free-standing properties in the street, and was likely to have been built in the 1920s, he said.

A resident of the house next door, which the roof collapsed onto, said she hadn't been allowed inside yet to see what damage had occured and had been instructed to keep at a distance from the property.